Subjective Loudness and Its Physical Correlate

According to the physical correlate theory, judgments of sensory intensity are based upon learned estimates of physical magnitudes correlated with changes in sensory stimulation rather than built-in neural functions. Relative loudness judgments are considered to be derived from familiarity with the effects of distance upon neural input. The following consequences of theory each have experimental support: (1) half-loudness judgments are numerically equivalent to estimates of the effect of doubling distance from the sound source; (2) equal stimulus ratios produce equal loudness ratios; (3) under ideal conditions, one-quarter sound intensity equals half-loudness; (4) the rules above apply not only for sounds produced by external sources, but also for self-generated sounds; (5) reverberation modifies loudness in specified ways; (6) new loudness scales are established by teaching of new physical correlates. This theory is placed in historical perspective, and related to evidence from other modalities.